Methods of synchronizing a personal handy-phone system station and phase lock loops

ABSTRACT

The present invention provides methods of synchronization, personal handy-phone system stations, and phase lock loops. Synchronization of a personal handy-phone system station with a telecommunication network, and another communication station are provided. One method of synchronization comprises: providing a counter configured to generate a plurality of counter values; storing a first counter value; detecting a reference event; latching a second counter value responsive to the detecting of the reference event; comparing the first counter value and the second counter value to detect phase drift; and compensating for phase drift responsive to the comparing.

RELATED PATENT DATA

This patent resulted from a continuation application of U.S. patentapplication Ser. No. 08/906,531, filed Aug. 5, 1997, now U.S. Pat. No.6,016,331 entitled “Methods of Synchronization, Personal Handy-PhoneSystem Stations and Phase Lock Loops”, naming Denis Archambaud et al. asinventors, the disclosure of which is incorporated by reference.

TECHNICAL FIELD

The present invention relates to methods of synchronization, personalhandy-phone system stations and phase lock loops.

BACKGROUND OF THE INVENTION

The benefits of a wireless communication network are readily recognized.The ability to transmit and receive either voice or peripheral (i.e.,facsimile) messages in mobile applications has been utilized in numerousapplications.

Wireless communications systems include cellular systems which haveparticularly enjoyed expansive popularity. Cellular systems generallycomprise a base station and a plurality of portable stations. Cellularsystems offer a radius of approximately 1-15 km per base station, andtraditionally provide coverage for cities, railways and main roads.However, existing cellular systems typically utilize a service networkwhich is distinct from the existing network (e.g., Public SwitchedTelephone Network (PSTN) or Integrated Services Digital Network (ISDN)).

Other wireless communication protocols have been introduced to providebenefits over existing cellular wireless technologies. Suchcommunication protocols provide benefits of interfacing directly withand utilizing the existing digital network. Such direct interfacingcapabilities eliminate the need for a distinct switching system.

One such communication system is the personal handy-phone system (PHS).The personal handy-phone system is a digital cordless telephone systemthat offers integrated telecommunication services, such as voice anddata, via a universal radio interface. The personal handy-phone systemoffers digitalization of the communication system. In particular, thedigital personal handy-phone system offers improved quality andeffective use of frequencies.

Personal handy-phone systems comprise at least one base station and aplurality of corresponding personal stations. The personal handy-phonesystem offers flexible inter-connectability wherein connection of apersonal station with a plurality base stations at various locationssuch as the office, home, or outdoors is possible. The PHS standard isset forth by the Telecommunications Technical Committee of Japan in“Personal Handy Phone System”, Japanese Telecommunications SystemStandard, RCR-STD 28.

The personal handy-phone system also offers connectability with existingcommunications networks. Connection is possible with analog telephonenetworks as well as digital networks.

Personal handy-phone systems typically comprise a plurality of personalstations (PS), also referred to as handsets, and base stations, alsoreferred to as cell stations (CS). Personal handy-phone systems aredesigned to provide wireless multimedia communications, terminalmobility, and complete two way communications. Personal handy-phonesystems utilize a micro-cell structure. Personal stations and basestations of the personal handy-phone system are configured to transmitand receive data via a plurality of data packets, also referred to asslots.

The base stations may be of a low power output type (i.e., 10 mW)generally for indoor applications, or a standard power output type(i.e., 20 mW) or high power output type (i.e., 100-500 mW) for outdoorapplications. Group control functions may be implemented to increasecommunication channels in an area with heavy traffic whereby multiplebase stations are controlled via the same control channel. Such stationsmay be arranged in a master/slave configuration.

Radio interfaces of the base stations and personal stations individuallyhave four-channel time division multiple access capability with timedivision duplexing (four-channel TDMA-TDD). The implementation of TDMAand TDD in accordance with the personal handy-phone system communicationstandard necessitates synchronization of the personal stations and thecorresponding base station.

Individual base stations are synchronized with the appropriatetelecommunications network to ensure reliable communicationstherebetween. Individual ones of the slave base stations aresynchronized with the master base station in master/slaveconfigurations.

Reference signals provided by conventional telecommunication networks(e.g., Integrated Services Digital Network) are typically unreliableinasmuch as phase drift is frequently experienced in such referencesignals. Further, other reference signals may also experience phasedrift during communications between the devices. It is preferred toperiodically analyze the synchronization of the communication devices toverify the correct timing of the devices and compensate for phase drift.

Conventional synchronization techniques utilize hard-wired circuitry tocompensate for phase drift and assure synchronization. However, thesetechniques are designed for a specific use and fail to provideflexibility to support a plurality of applications.

Therefore, there exists a need for assuring synchronization of thecommunication stations of a personal handy-phone system and providingflexibility for assuring synchronization in a plurality of applications.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a block diagram of a personal handy-phone system comprising abase station and a plurality of personal stations in radio communicationwith the base station.

FIG. 2 is an illustrative view of a frame structure according to thepersonal handy-phone system communication protocol.

FIG. 3 is an illustrative view of the structure of a control slotaccording to the personal handy-phone system communication protocol.

FIG. 4 is a block diagram of one embodiment of a base station.

FIG. 5 is a block diagram of one embodiment of a personal station.

FIG. 6 is a block diagram of an embodiment of the clock generator of thebase station shown in FIG. 4.

FIG. 7 illustrates a flow diagram of a control process for analyzingreference events for implementing synchronization operations inaccordance with one embodiment of the present invention.

SUMMARY OF THE INVENTION

The disclosure provides a phase lock loop and methods for implementingsynchronization functions. A plurality of personal handy-phone systemframes are synchronized to one of a plurality of reference signals. Asis discussed in detail below, the particular reference signal utilizedfor synchronization is selected by software via a processor. Further,the processor is configured to monitor and compensate for any phasedrift detected within the reference signal.

According to a first aspect of the present invention, a method ofsynchronization comprises: providing a counter configured to generate aplurality of counter values; storing a first counter value; detecting areference event; latching a second counter value responsive to thedetecting of the reference event; comparing the first counter value andsecond counter value to detect phase drift; and compensating for phasedrift responsive to the comparing.

In accordance with a second aspect of the present invention, a method ofsynchronizing a personal handy-phone system station comprises: receivinga reference signal; generating a bit rate signal within the personalhandy-phone system station; detecting a plurality of reference eventswithin the reference signal; and adjusting the bit rate signalresponsive to the detecting of the reference events.

Another aspect of the present invention provides a method ofsynchronizing a personal handy-phone system station comprising:receiving a reference signal having a plurality of reference events;generating a plurality of counter values; first detecting an initialreference event; following the first detecting, storing a first countervalue; second detecting a subsequent reference event; following thesecond detecting, storing a second counter value; comparing the firstcounter value and the second counter value; third detecting phase driftwithin the reference signal responsive to the comparing of the firstcounter value and the second counter value; and compensating for phasedrift responsive to the third detecting.

An additional aspect of the present invention provides a personalhandy-phone system station comprising: an input configured to receive areference signal; a clock generator comprising: an oscillator configuredto generate a timing signal; a counter configured to generate a sequenceof counter values responsive to the timing signal; and an output latchconfigured to selectively store a plurality of counter values; and aprocessor coupled with the clock generator, the processor beingconfigured to compare the counter values and compensate for phase driftwithin the reference signal.

Yet another aspect of the present invention provides a phase lock loopcomprising: an input operable to receive a reference signal; a clockgenerator configured to generate a bit rate signal; and a processorcoupled with the input and the clock generator, the processor beingconfigured to detect phase drift within the reference signal andcompensate for phase drift in the bit rate signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a personal handy-phone system (PHS) 10 is shown.The illustrated personal handy-phone system 10 comprises a base station12 and a plurality of personal stations 14. Base station 12 is typicallycoupled with a telecommunication network 13, such as an ISDN or PSTN. Agiven cell may contain plural base stations 12 depending upon thetraffic volume to be handled. In an exemplary embodiment, a master basestation and plurality of slave base stations are provided for suchincreased transmission capabilities. FIG. 1 shows but one of such basestations.

The personal handy-phone system is configured to allow movement of thepersonal stations 14 throughout a cell during communication with arespective base station 12. Base stations 12 are configured to handovercommunications with a corresponding personal station 14 to an adjacentbase station 12 responsive to the movement of the personal station 14.Personal stations 14 are also configured provide mobile radiocommunications directly to other personal stations 14.

Base station 12 includes a first antenna configuration 42 comprisingdual antennas for providing antenna diversity. Antenna diversityprovides improved spectral efficiency. Base station 12 is configured toreceive communications from personal stations 14 via one of the antennasof configuration 42, which provides the best signal. Personal stations14 include respective antenna configurations 52 for providing radiofrequency communications.

The personal handy-phone system communication protocol (i.e.,four-channel TDMA-TDD) provides one control channel and three trafficchannels for an individual base station 12. Providing time divisionmultiple access capability with time division duplexing avoids the needfor paired frequency bands.

Referring to FIG. 2, a typical radio channel structure 20 is shown. Theradio channel structure comprises a frame 22 which comprises a pluralityof slots 24 (eight slots are shown defining one frame in FIG. 2). Inparticular, one five millisecond TDMA-TDD frame within the radio channelstructure 20 includes four slots for base station transmission, and fourslots for personal station transmission. Communications from basestation 12 to respective personal stations 14, referred to herein asdownlink communications, occur within the first four slots 24 of theframe 22 (i.e., slots 1-4). Communications from respective personalstations 14 to the base station 12, referred to herein as uplinkcommunications, occur within the subsequent four slots of theillustrated frame 22 (i.e., slots 5-8).

The personal handy-phone system communications protocol provides for acontrol channel (CCH) and a communication channel, also referred to as atraffic channel (TCH). The control channel (CCH) may be one of a varietyof formats in accordance with the personal handy-phone system standard.The control channel is composed of a combination of a common controlchannel (CCCH) and an associated control channel (ACCH). The commoncontrol channel and associated control channel make up a singlededicated channel providing improved performance in conditions ofintermittent communications. The traffic channel is utilized to transmituser traffic information.

Referring to FIG. 3, a typical control slot 30 is shown. Control slot 30comprises 224 bits, thus allowing sixteen guard bits intermediateadjacent slots. A ramp field (R) 32 of control slot 30 comprises fourramp bits and a start symbol field (SS) 34 comprises two start symbolbits. A preamble 36 follows the start symbol field 34 and comprisessixty-two bits.

Control slot 30 additionally comprises a unique word (UW) 38 ofthirty-two bits which follows the preamble 36. The unique word 38 is apredetermined pattern which establishes transmit and receive timing. Achannel identifier field (CI) 40 of four bits is next provided after theunique word 38. A common access channel field (CAC) 42 and a cyclicredundancy check field (CRC) 44 respectively follow the channelidentifier field 40.

Common access channel field 42 may comprise one of a plurality ofchannels. For example, field 42 is selectively a broadcast channel(BCCH), paging channel (PCH) or signalling control channel (SCCH) asdefined within the PHS standard.

The broadcast channel is a one-way downlink channel to report controlinformation from the base station 12 to the personal station 14 withwhich it is communicating. It is utilized to transmit informationrelated to channel structure and system information. The paging channelis a one-way downlink, point-to-multipoint channel that simultaneouslytransmits identical information to individual cells or a wide area ofmultiple cells (the paging area) from a base station 12 to the personalstation 14. The signalling control channel is a bi-directional,point-to-multipoint channel that transmits information needed for callconnection between the base station 12 and the personal station 14. Thesignalling control channel transmits independent information to eachcell. The uplink channels are random access.

Synchronization of the communications system is a concern for ensuringreliable transmission of data, especially in conjunction with the use ofTDMA and TDD. In accordance with aspects of the present invention,specified reference events are utilized for ensuring synchronization ofbase stations 12 and personal stations 14 within the personalhandy-phone system 10. Further, synchronization of base station 12 andtelecommunication network 13 ensures reliable communicationtherebetween.

According to one preferred method of the present invention, variousreference events specified by software are utilized to assuresynchronization. Referring again to FIG. 1, a first reference event isused for synchronization between the telecommunication network 13 andthe base station 12. A reference signal provided by telecommunicationnetwork 13 is applied to base station 12 for assuring synchronization.

Base station 12 is configured to transmit a second reference event whichis received within corresponding personal stations 14. Personal stations14 are configured to synchronize to the second reference event generatedby the appropriate base station 12.

In master/slave base station PHS system configurations, the slave basestations are synchronized with the timing of the master base station. Inparticular, the master base station generates a third reference eventfor providing synchronization to corresponding slave base stations.

Referring to FIG. 4 and FIG. 5, respective embodiments of base station12 and one of personal stations 14 are shown. The illustrated basestation 12 and personal station 14 respectively comprise clockgenerators 50, 60, antenna configurations 41, 52, transceivers 45, 54,central processing units (CPUs) 46, 56, memory devices 47, 57 andregisters 48, 58.

Transceiver 45 includes an input and output coupled with antennaconfiguration 41 via connection 43. Central processing unit 46 includesan input and output coupled with telecommunication network 13.Transceiver 54 includes an input and output coupled with antennaconfiguration 52 via connection 53. Central processing unit 56 includesan input and output coupled with interface 15. The inputs are operableto receive a reference signal.

Base stations 12 and personal stations 14 individually includerespective phase lock loops 51, 61 for verifying integrity of thereference signal and providing synchronization of the communicationdevices within the personal handy-phone system. Phase lock loops 51, 61detect and compensate for phase drift within the particular referencesignal being utilized for synchronization.

In the illustrated embodiment, phase lock loops 51, 61 respectivelycomprise at least one selected input, one of clock generators 50, 60,and one of central processing units 46, 56. Central processing units 46,56 are also referred to as processors.

Antenna configurations 41, 52 are utilized to implement two-waycommunication of radio frequency signals. Antenna configurations 41, 52are coupled with appropriate switching circuitry for providing bothtransmission and reception operations.

Transceivers 45, 54 contain appropriate transmission circuitry forproviding modulation of the appropriate carrier frequency signal by thebaseband signal, and demodulation circuitry for recovering the basebandsignal from the received radio frequency signals.

Central processing units 46, 56 provide control information torespective transceivers 45, 54 for controlling the transmissionoperations. Further, central processing units 46, 56 monitor controlinformation from transceivers 45, 54 during receive modes of operation.

Central processing units 46, 56 are configured via operational softwarecode to also function as TDMA processors to perform manipulationoperations providing the transmission data and control information intoslots and frames in accordance with the personal handy-phone systemcommunications protocol. Similarly, central processing units 46, 56 areconfigured via software code to retrieve the data and controlinformation from the slots within the baseband signals received withintransceivers 45, 54.

Central processing units 46, 56 are coupled with respective memorydevices 47, 57. Software code for configuring central processing units46, 56 is stored in respective memory devices 47, 57. In one embodiment,memory devices 47, 57 comprise volatile memory permitting flexibility ofstoring different operational software code. In an alternativeembodiment, memory devices 47, 57 comprise a ROM or other non-volatilememory for storing software code utilized by central processing units46, 56.

Data information (e.g., voice, peripheral) may be applied to thetelecommunication network 13. Certain control information may be appliedto registers 48, 58 and clock generators 50, 60. Clock generators 50, 60are configured to output control information to central processing units46, 56 via registers 48, 58. Registers 48, 58 are configured to providebi-directional communications. As discussed in detail below, clockgenerators 50, 60 are configured to generate a bit-rate signal utilizedfor timing within respective base station 12 and personal station 14.Clock generators 50, 60 assist with the implementation of digital phaselock loop operations for eliminating drift and providingsynchronization.

Central processing unit 46 of base station 12 is coupled withtelecommunication network 13 and bi-directional communications areprovided therebetween. Base station 12 is operable to apply datareceived from corresponding personal stations 14 to telecommunicationnetwork 13. Further, telecommunication network 13 applies data andcontrol information to base station 12. Such control information mayinclude synchronization information.

Central processing unit 56 of personal station 14 is coupled withinterface 15. Interface 15 contains receiving interfaces such as amicrophone or a port for receiving voice or facsimile data. Interface 15also includes interfaces such as a LCD or LED display for conveyingreceived visual information and a speaker for conveying received audioinformation.

According to the preferred embodiment, respective clock generators 50,60 are implemented utilizing the embodiment of the clock generator 50shown in FIG. 6. In particular, a preferred clock generator may beconfigured for use in either a base station 12 or personal station 14.Although FIG. 6 is described herein with reference to implementation ofclock generator 50 within a base station 12, it is to be understood thatthe illustrated embodiment of the clock generator 50 may also beimplemented as clock generator 60 with in a personal station 14 of thepersonal handy-phone system.

The illustrated clock generator 50 comprises an input latch 70, counter72, digital to analog converter 74, oscillator 75, frequency divider 76,output decoder 77 and output latch 78. The clock generators operate togenerate timing signals regardless of whether implemented within a basestation 12 or personal station 14.

Oscillator 75 is configured to generate a 19.2 MHz clock timing signalin compliance with the personal-handy phone system standard. The 19.2MHz timing signal is utilized as a timing reference within respectiveones of the communication stations 12, 14. Oscillator 75 is implementedas a voltage-controlled oscillator in accordance with one aspect of thepresent invention.

The output 19.2 MHz timing signal is applied to frequency divider 76.Frequency divider 76 operates as a divide by 2 divider for providing a9.6 MHz systems clock signal in accordance with the personal handy-phonesystem standard. The 9.6 MHz systems clock signal is applied to counter72.

Counter 72 and output decoder 77 operate to further divide the frequencyof the systems clock signal. In particular, a preferred embodiment ofcounter 72 is configured to sequentially count a plurality of countervalues from 0 to 24. Output decoder 77 is configured to generate andoutput a logic low signal responsive to the counter values of counter 72being 0-12. Output decoder 77 is configured to generate and output alogic high signal responsive to the counter values of counter 72 being13-24. Thus, counter 72 and output decoder 77 operate as a divide by 25frequency divider. More specifically, output decoder 77 outputs a 384kHz signal responsive to the systems clock signal being a 9.6 MHzsignal. The 384 kHz signal is utilized as a bit rate signal inaccordance with the personal handy-phone system standard. The 384 kHzsignal is applied to bit counter 79 for use within the respectivecommunication station 12, 14. In one embodiment, bit counter 79 isoperable to sequentially count from 0 to 239 corresponding to the 240bit frames specified by the personal handy-phone system communicationstandard.

Clock generators 50, 60 operate to output the clock signals (e.g.,timing signals, bit-rate signals) for utilization within base station 12and personal station 14, respectively. Base station 12 and personalstation 14 are configured for synchronization with a reference signal.In particular, central processing units 46, 56 operate in conjunctionwith a respective clock generator 50, 60 to provide synchronization ofthe clock signals with the reference signal.

Still referring to FIG. 6, synchronization operations are discussedbelow. Central processing units 46, 56 of communication stations 12, 14are configured to detect a plurality of reference events forsynchronization purposes. In the described embodiments, centralprocessing units 46, 56 receive the reference signal fromtelecommunication network 13, base station 12, or a master base station12 in a master/slave base station configuration. Central processingunits 46, 56 are configured via software code to detect reference eventswithin one of a plurality of reference signals, some of which aredescribed in detail below.

Synchronization operations are discussed with reference to clockgenerator 50 of base station 12. It is to be understood that clockgenerator 60 of personal station 14 operates in a similar manner as thatof clock generator 50 in one embodiment of the present invention.

Following the detection of reference events within a reference signal bycentral processing unit 46, corresponding counter values of counter 72are compared for detecting drift within the reference signal. Morespecifically, central processing unit 46 outputs a latch enable signalto output latch 78 responsive to the detection of an initial referenceevent. Output latch 78 is configured to latch the current counter valueof counter 72. The latched counter value is available to registers 48coupled with central processing unit 46. The counter value is storedwithin registers 48 for future comparison. This counter value isreferred to as the reference counter value.

Thereafter, following the detection of a subsequent reference event,output latch 78 latches another counter value from counter 72 responsiveto receiving a subsequent latch enable signal from central processingunit 46. This current counter value is applied to registers 48. Centralprocessing unit 46 is operable to read and compare the current countervalue with the previously-stored (i.e., reference) counter value.Variance between the reference counter value and the current countervalue indicates the presence of drift within the reference signal.

In an alternative embodiment, output latch 72 is configured to receivethe reference signal and detect the presence of a reference eventtherein. Responsive to the detection of a reference event, output latch78 latches the current counter value of the counter 72. According tofurther aspects of the present invention, output latch 78 isadditionally configured to store bit values from bit counter 79.Responsive to the detection of a reference event, output latch 78latches the current bit value from counter 79 in addition to latchingthe current counter value from counter 72.

According to one aspect of the present invention, clock generator 50 isconfigured to compensate for phase drift through the manipulation of thecounter value generated by counter 72. Central processing unit 46 isoperable to load the previously-stored reference counter value, oranother counter value, into counter 72 via input latch 70 responsive tothe detection of phase drift. Central processing unit 46 outputs acontrol signal to input latch 70 responsive to the presence of drift.Loading of the reference counter value into counter 72 resets thecounter and compensates for phase drift within the reference signal.Such loading and resetting aligns the counter 72 with the referenceevents of the received reference signal.

According to another aspect of the present invention, oscillator 75comprises a voltage-controlled oscillator. Responsive to the detectionof phase drift, central processing unit 46 is operable to output digitalcontrol signals to digital to analog converter 74. Analog controlsignals, corresponding to digital control signals provided by centralprocessing unit 46, are applied to oscillator 75. Such control signalsoperate to vary the 19.2 MHz timing signal generated by oscillator 75.In particular, adjustment of the voltage via the control signals isutilized to compensate for phase drift within the reference signal. Theadjusted output timing signal is applied to frequency divider 76,counter 72, and output decoder 77 to provide for the generation of therespective system clock signal and the bit rate signal.

Referring to FIG. 7, the above mentioned software for providing thecomparison of the counter values to detect phase drift and thecompensation thereof is described with reference to a flow chart. It ispreferred to implement such control process by software to increaseflexibility of the selection of reference signals and reference eventsutilized to provide synchronization and implementation of the digitalphase lock loop operations. The flow chart describes a process that isimplemented by digital circuitry in an alternative embodiment.

Although FIG. 7 is described with reference to central processing unit46 of base station 12, it is to be understood that central processingunit 56 of personal station 14 is configured to execute similar softwarecode in accordance with embodiments of the present invention.

First, in step 90, central processing unit 46 monitors for the presenceof a reference event. If no reference event is detected, centralprocessing unit 46 continues to monitor for the presence of a referenceevent. Following the detection of a reference event, central processingunit 46 proceeds to step 92 where central processing unit 46 outputs alatch enable control signal. This enable signal is applied to outputlatch 78 for latching the current counter value. The current bit valuemay also be latched responsive to this control signal. The centralprocessing unit 46 next proceeds to step 94 where the stored referencecounter value is read by the central processing unit 46. Next, centralprocessing unit 46 proceeds to step 96 where the latched current countervalue is read by the central processing unit 46.

Central processing unit 46 proceeds to step 98 where the referencecounter value is compared with the current counter value. If thereference counter value is equal to the current counter value thencentral processing unit 46 proceeds to step 90 to monitor for thedetection of a subsequent reference event. If the reference countervalue is not equal to the current counter value, the central processingunit 46 proceeds to step 100. While performing step 100, centralprocessing unit 46 outputs a counter value to input latch 70 forapplication to counter 72 for compensating for phase drift. Theoutputted counter value may be the reference counter value. Thereafter,central processing unit 46 proceeds to step 90 to monitor for thepresence of another reference event.

As previously mentioned, a plurality of reference events may be utilizedto provide synchronization. In one implementation of the presentinvention, base station 12 is synchronized with telecommunicationnetwork 13 assuring proper transfer of data therebetween. In particular,telecommunication network 13 outputs a frame synchronization signal.According to personal handy-phone system protocol, frames 20 areindividually 5 milliseconds. Telecommunication network 13, such as anISDN network, typically provides a 200 Hz frame synchronization signalwhich corresponds to the 5 millisecond PHS frame format. In thisdescribed implementation, the frame synchronization signal is utilizedas the reference signal for synchronizing base station 12. The cycles ofthe 200 Hz frame synchronization signal correspond to the beginning of aPHS frame and are utilized as reference events in accordance with afirst implementation of the invention.

Personal stations 14 are typically synchronized with a correspondingbase station 12. As described above, the base stations 12 transmit slotsto the personal stations 14 in accordance with the personal handy-phonestandard. Such slots include a unique word 38. The unique word 38 isutilized for synchronization of the personal stations 14 to a basestation 12 according to one aspect of the present invention. The uniquewords 38 are utilized as reference events for synchronization. Inparticular, phase drift may be identified within the reference signaland compensated for in accordance with the previously-described methodsthrough the utilization of unique words 38 as the reference events.

In master/slave base station configurations, the master station ispreferably configured to apply a 200 Hz frame synchronization signal tocorresponding slave stations. The frame synchronization signal providedby the master base station is utilized as the reference signal having aplurality of reference events (i.e., the individual cycles of the 200 Hzframe synchronization signal).

In an alternate embodiment, a unique word 38 transmitted from the masterbase station is utilized for synchronization of the slave base stations.In such embodiments, the slave base stations are configured to operateas personal stations during the transmission of the unique word 38 fromthe master base station. The received unique words 38 are utilized asreference events by the respective slave base stations in thisembodiment.

The current value of counter 72 is latched responsive to the receptionof the appropriate reference event (e.g., cycle of the framesynchronization signal, unique word). The latched current counter valueis compared with the stored current value in accordance with preferredmethods of the present invention described above.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A synchronization method comprising: receiving areference signal having a plurality of reference events; generating atiming signal independent of the reference signal; generating a bit ratesignal responsive to the timing signal, the generating comprising:utilizing a counter, generating a plurality of counter values responsiveto the timing signal; and decoding the counter values to establish thebit rate signal; detecting the plurality of reference events within thereference signal after the receiving; and adjusting the bit rate signalresponsive to the detecting of the reference events.
 2. The methodaccording to claim 1 wherein the reference events individually comprisea unique word of a personal handy-phone system slot.
 3. The methodaccording to claim 1 further comprising utilizing the timing signal as atiming reference within a personal handy-phone system station.
 4. Themethod according to claim 1 wherein the generating of the bit ratesignal comprises: decoding the counter values to establish the bit ratesignal having a frequency different than a frequency of the timingsignal.
 5. The method according to claim 1 wherein the adjustingcomprises resetting a current counter value of the counter.
 6. Themethod according to claim 1 wherein the generating of the timing signalcomprises using a voltage controlled oscillator.
 7. The method accordingto claim 6 wherein the adjusting comprises controlling a voltage of acontrol signal applied to the voltage controlled oscillator.
 8. Themethod according to claim 1 further comprising detecting phase driftresponsive to the detecting of the reference events.
 9. The methodaccording to claim 8 wherein the adjusting is responsive to thedetecting of phase drift.
 10. The method according to claim 8 whereinthe detecting phase drift comprises: storing a first counter valueresponsive to detecting an initial reference event; latching a secondcounter value responsive to detecting a subsequent reference event; andcomparing the first counter value and the second counter value.
 11. Themethod according to claim 10 wherein the comparing of the counter valuesand the adjusting of the bit rate signal comprise using a processor. 12.A phase lock loop comprising: an input operable to receive a referencesignal having a plurality of reference events; a clock generatorconfigured to generate a timing signal independent of the referencesignal and to generate a bit rate signal responsive to the timingsignal, the clock generator comprising: a counter configured to count aplurality of counter values; and an output decoder operable to generatethe bit rate signal responsive to the counter values; and a processorcoupled with the input and the clock generator, the processor beingconfigured to detect the reference events, and to detect phase driftwithin the reference signal responsive to the detection of the referenceevents and to adjust the bit rate signal to compensate for the phasedrift.
 13. The phase lock loop according to claim 12 wherein the outputdecoder is operable to generate the bit rate signal having a frequencydifferent than a counting frequency of the counter.
 14. The phase lockloop according to claim 12 wherein the processor is configured to applya reference counter value to the counter to compensate for phase drift.15. The phase lock loop according to claim 12 wherein the clockgenerator further comprises a voltage control oscillator configured togenerate the timing signal.
 16. The phase lock loop according to claim15 wherein the processor is configured to adjust a voltage of a controlsignal applied to the voltage controlled oscillator.
 17. The phase lockloop according to claim 15 wherein the processor is configured tocompare the plurality of counter values to detect phase drift.
 18. Thephase lock loop according to claim 12 wherein the reference eventsindividually comprise a unique word of a personal handy-phone systemslot.
 19. The phase lock loop according to claim 12 wherein thereference signal is generated by a telecommunication network.
 20. Asynchronization method comprising: receiving a reference signal having aplurality of reference events; generating a timing signal independent ofthe reference signal; generating a bit rate signal responsive to thetiming signal; detecting the plurality of reference events within thereference signal after the receiving; detecting phase drift responsiveto the detecting of the reference events, the detecting phase driftcomprising: storing a first counter value responsive to detecting aninitial reference event; latching a second counter value responsive todetecting a subsequent reference event; and comparing the first countervalue and the second counter value; and adjusting the bit rate signalresponsive to the detecting of the reference events.
 21. Thesynchronization method according to claim 20 wherein the comparing ofthe counter values and the adjusting of the bit rate signal compriseusing a processor.